To include small terrestrial gastropod species (under 5 mm) in faunistic and ecological studies
on the malacofauna it is necessary to take samples of the litter layer. The established practise
is to take 3–5 litres of litter or foerna. The method how to separate shells from other mineral
matter has been well known for many years (e.g. GEYER 1927, LOŽEK 1956). In particular this
method is based on the fact that empty shells are filled with air and therefore float on the
water surface, whereas other mineral matter sinks down. However, in mires this method is not
optimal. Moreover in fens with a higher portion of fine clay particles it is not applicable at all.
Of course, the alternative method of direct picking is insufficient in mires, due to the small
size of the majority of species (maximum adult size of ca. 10 snail species ranges from 1.6 to
2 mm). Besides that, most of the rare, endangered and indicator species are of smaller size
(e.g. Vertigo spp.).
In mires, empty shells are filled with water. Therefore, both empty shells and living
animals sink down in the course of washing. The present method is based on this fact.